Virtual eXtensible Local Area Network (VXLAN) adopts a technology in which a layer 2 packet is encapsulated according to a layer 3 protocol. For example, an outer tunnel with a User Datagram Protocol (UDP) format is used as a data path layer, and packet data are transmitted as payloads.
Since the outer layer of the payloads adopts UDP transmission, the payloads can be transmitted in a layer 2 network and a layer 3 network fluently, so that the layer 2 network may cover the layer 3 network. A covering virtual network is called an overlay network, and a covered physical bearer network is called an underlay network.